The present invention relates to an image pickup lens system and particularly, to an image pickup lens system which is comprised of one lens and used in an image pick-up device (e.g., an image-inputting CCD camera) utilizing a solid image-pickup element such as CCD, CMOS and the like mounted on a potable computer, a visual telephone and the like, and which can ensure a wider angle of view and can be reduced in size and weight.
In recent years, multimedia have been developed remarkably, and for example, the demand for a camera utilizing a solid image-pickup element such as CCD, CMOS and the like, e.g., a CCD camera, mounted on a portable computer, a visual telephone and the like, is being increased remarkably. Such a CCD camera is required to be mounted in a limited space and for this reason, it is desired that the CCD camera is small in size and lightweight.
Therefore, it is also desired that an image pickup lens system used in such a CCD camera is likewise small in size and lightweight.
A one-lens system using a single lens is conventionally used as such an image pickup lens system.
FIG. 1 shows a prior art of a one-lens system using a single lens. This one-lens system comprises a lens body 15 having a first face formed as a convex face and a second face formed as a convex face and has a positive power. The lens body 15 is put in position at inside part of one end of a lens barrel 16. A diaphragm 17 expanding inwardly from the lens barrel 16 is disposed at the one end of the cylinder 16 and holds the lens body 15 by putting it between the diaphragm 17 and a press member 18 disposed at a location on a rear side of the lens body 15.
Moreover, as showing in FIG. 2, an image-pickup circuit 20 having an image-pickup element 19 such as CCD, CMOS and the like, is put in position at a location of the second face of the lens body 15 by adjusting an optical axis 21 of the lens body 15 and an optical axis 22 of the image-pickup element 19.
However, as showing in FIG. 2, the conventional image pickup lens system of such arrangement suffers from the following problems: When the lens body 15 inserts in the lens barrel 16, it is necessary to adjust an optical axis 23 of both of the lens barrel 16 and the diaphragm 17 and the optical axis 21 of the lens body 15. Accordingly, a very high accuracy of assembling and so much long assembling time are necessary and the manufacture cost is increased. If the accuracy of the adjusting optical axes is deteriorated, a desired optical performance of lens is also deteriorated.
To solve such problems, some image pickup lens systems disclosed, for example, in Japanese Patent Application Laid-open Nos.6-250083 and 5-273461.
Any of these image pickup lens systems disclosed in the above Patent Applications is comprised of a lens body and a circular groove which is formed at a location of the center of the optical axis direction of the outer cylindrical surface of the lens body, has a wedge shape section and works as a diaphragm.
However, any of such conventional image pickup lens systems suffers from a problem that F number of the lens system is more than 10 so that the lens system is very dark. The image pickup lens systems disclosed in Japanese Patent Application Laid-open No.6-250083 is used in a document reader device such as a scanner and the like, and the image pickup lens systems disclosed in Japanese Patent Application Laid-open No.5-273461 is used in a film with a lens, and these conventional image pickup lens systems can be applied to the document reader device and the film with a lens without any problem, but they can not be applied to a potable computer, a visual telephone, a cellular phone and the like, because these conventional systems are too dark.
Moreover, any of such conventional image pickup lens systems suffers from a problem that it is very difficult to lighten the lens system, because they consist of a lens body with a circular groove and they have no diaphragm. Moreover, they suffer from a problem that a stray light such as a flare and a ghost and the like easily occurs and this stray light is not eliminated completely. If a lens system becomes lighter, the problem of the occurrence of the stray light is more severe. Therefore, conventional image pickup lens systems are not used in a solid image-pickup element.
Accordingly, it is an object of the present invention to provide an image pickup lens system, in which the numbers of the elements of the image pickup lens system are decreased, which can be produced easily and speedy, and in which a optical performance concerning the image pickup lens system is increased.
To achieve the above object, according to the present invention, there is provided an image pickup lens system comprising a lens body having a positive power and a diaphragm which is unified with the lens body at a location between the first face and the second face of the lens body and of which inner cylindrical surface is put in position at a location of the inside of the lens body.
With the above feature, the lens body and the diaphragm are unified each other. Thus, the numbers of the elements of the image pickup lens system are decreased and the image pickup lens system can be produced accurately. Moreover, when the lens body and the diaphragm are unified each other, both optical axes of the lens body and the diaphragm can be very accurately adjusted and automatically adjusted. Thus, a work to adjust accurately those optical axes is not necessary so that the lens body and the diaphragm can be produced easily and speedy. Moreover, by disposing the actual diaphragm, this invention can prevent the occurrence of the stray light such a flare and a ghost and the like and can actually remove the stray light if it occurs.
According to another present invention, there is provided an image pickup lens system comprising the diaphragm is unified with a lens barrel.
With the above feature, the diaphragm and the lens barrel are unified each other. Thus, the numbers of the elements of the image pickup lens system are more decreased and the image pickup lens system can be produced more easily and speedy.
According to another present invention, there is provided an image pickup lens system comprising the inner cylindrical surface of the diaphragm has an acute angle end at a location of the first face side portion or the second face side portion of the lens body.
With the above feature, the inner cylindrical surface of the diaphragm has an acute angle end at a location of the first face side portion or the second face side portion of the lens body. Thus, the diaphragm provides its appropriate function.
According to another present invention, the diaphragm is made of a material which has a similar or almost the same heat conductivity of the one of a molding die for molding the lens body.
With the above feature, the diaphragm is made of a material which has a similar or almost the same heat conductivity of the one of a molding die for molding the lens body. Thus, during a cooling step of the molding process of the lens body, both of the cooling temperature of the inner part and the outer part contacting with inner surface of a molding die of the lens body can be kept almost the same so that whole part of the lens body can be cooled almost uniformly. Therefore, a refractive index is kept uniformly in the whole inner part of the lens body without any unevenness so that a image pickup lens system having a stable optical performance can be provided.
According to another present invention, there is provided an image pickup lens system comprising the diaphragm has a light shade which extends from diaphragm to the first face of the lens body along the outer cylindrical surface of the lens body.
With the above feature, the diaphragm has the light shade which extends from diaphragm to the first face of the lens body along the outer cylindrical surface of the lens body. Thus, the light shade can remove an incident ray and a stray light on outer cylindrical surface of the lens.